1. Field of the Invention
The present invention relates to the acetoacetylation of saccharides with diketene using enzymatic methods.
2. Description of Background and Related Art
Saccharides, both modified and unmodified, are used widely as additives to paper, paints, construction materials, and personal care products. In many applications, it is desirable to modify the chemical structure of a saccharide in order to have additional functionalities. For instance, when a saccharide is acetoacetylated by grafting a bidentate ligating group onto the saccharide, the acetoacetylated saccharide can form complexes with metal ions, such as Ca2+, Fe3+, and Al3+ and therefore remove metal ions from another medium.
Acetoacetylated saccharides have been synthesized using chemical methods. For instance, U.S. Pat. No. 4,708,821 to Shimokawa discloses a chemical method to synthesize acetoacetylated hydroxyethylcellulose (HEC). U.S. Pat. No. 5,360,843 to Edgar et al. discloses a chemical method to synthesize cellulose acetoacetates by contacting a cellulose material with diketene in a solvent system comprising lithium chloride and a carboxamide. U.S. Patent No. 5,565,037 to Sobotta et al. discloses a chemical reaction of glucose with diketene to prepare 1,2,5,6-diacetone-D-glucose . U.S. Pat. Nos. 3,361,585 and 3,342,806 disclose chemical methods of preparing starch-acetoacetalate.
U.S. Pat. application No. 09/564,575, filed May 5, 2000, discloses a process of making an esterified saccharide product using enzymes as a catalyst. It discloses that the reaction between alkyl ketene dimers and saccharides such as cellulosic or guar derivatives to make hydrophobically modified saccharides can be catalyzed by enzymes with high reaction yields. Also, when the chemical synthesis is catalyzed by enzymes, the reaction conditions are much milder than reactions without enzymes.
Enzymes have not been used as catalyst to prepare acetoacetylated saccharides. Therefore, it would be advantageous to use enzymes to catalyze reactions between saccharides and diketene to prepare acetoacetylated saccharides since such enzymatic reactions may have higher yields and lower processing costs due to milder reaction conditions.
The present invention is a process for producing acetoacetylated saccharides. The process comprising combining saccharide, diketene, and a catalytically effective amount of an enzyme as a reaction mixture under conditions wherein the enzyme catalyzes a reaction between the saccharide and diketene to form the acetoacetylated saccharide. The preferred enzymes are hydrolytic enzymes such as lipases, esterases, and proteases.